Link Claimed Between Spring Birth and Early Menopause

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This study found an association between spring births and earlier menopause, suggesting environmental factors during the season in which someone is born may influence reproductive patterns.

MODENA, Italy, May 11-Researchers here have suggested that if a woman's birthday falls in the spring her menopause is likely to begin a year earlier than for a woman born during autumn.

The birth-menopause relationship was proposed in a study published in the May issue of Human Reproduction. It found that menopause occurred earlier for women born between March and June (age 49.04 Â± 0.15 years) than it did for women born between September and December (49.97 Â± 0.14 years).

"Our data show that the timing of ovarian exhaustion can also be influenced by prenatal factors linked to seasons," concluded Angelo Cagnacci, M.D., an associate professor of obstetrics and gynecology at the University of Modena, and colleagues.

The finding is based on a retrospective multicenter study of 2,822 postmenopausal women who were treated at three different menopause clinics throughout Italy between January 1997 and December 2001. Women were included in the study only if menopause, defined as amenorrhea for greater than 12 months was easily identifiable.

Women who had undergone surgical menopause had been given medications that could interfere with the timing of menopause, or were receiving oral contraceptives during the menopausal transition were excluded from the study.

The women included in the study had an average age of 49.42 years at the time of menopause. Data were collected on their month and year of birth, age at menarche (but not the date), number of pregnancies, including miscarriages and stillbirths, menopausal status, date of last spontaneous menstrual period, use of estrogens, progestins or other hormonal aids during menopause transition, smoking status, body mass index, weight, education, and employment.

The researchers reported that season and month of birth remained an influential factor on age at menopause even after adjusting for age at menarche, body mass index, and life style factors, including smoking habit, level of education and type of job.

On average, there was about a 11-month difference between age at menopause for women born in spring compared with those born in the fall. The proportion of women with early menopause (age â‰¤40) was similar in women born in different seasons. However, the proportion of women with menopause at age â‰¥55 was higher in women born in the autumn (8.1%) than in spring (3.7%, p=0.013). Earliest menopause occurred for women born in March (48.9 Â± 0.25 years) and occurred latest for women with October birthdays (50.3 Â± 0.25 years).

The study suggests seasonal and environmental effects during prenatal development could impact one's fertility in adulthood, the researchers said. They speculated that environmental temperatures, sunlight, seasonally associated dietary changes, or exposures to infections may all influence a woman's adult fertility before she is even born.

"Our present data seem to indicate that women born in autumn develop better during their prenatal life and are born with a higher number of oocytes than women born in spring," the researchers wrote. The timing of one's prenatal development may help regulate "adult reproductive life and the timing of its termination."

Dr. Cagnacci added, "Mothers should be aware of this, considering that during pregnancy they are going to influence, not only the health of the newborn, but also the health and reproductive life of their child during adulthood."

Dr. Cagnacci and colleagues also suggested that the effect of seasons may differ in various geographic locations.

Scientists have investigated the relationships between season of birth and menstrual patterns before. Some researchers have theorized that environmental factors at play during the time of a woman's birth may affect hormone levels and influence not only her reproductive health, but potential breast cancer risk as well. However, no conclusive associations have been found between season of birth and reproductive patterns.

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